Grease-making process involving mechanical atomization



Aug. 23, 1960 E. 1 ARMSTRONG ET AL 950,249

GREASE-MAKING PROCESS INvCLvINC MECHANICAL ATCMIZATICN Filed Sept. 13, 1957 5 Sheets-Sheet l Aug. 23, 1960 E. l.. ARMSTRONG ErAL 2,950,249

GREASE-MAKING PROCESS INVOLVING MECHANICAL ATOMIZATION Filed sept. 13,1957 5 sheets-sheet 2 f Nozzle Swirl Chamber Flow Palhl 6 Swirl Replaceable Chamber Orifice Gap 53 S2 70 Body INVENTOR. ELnoN .ARMs'rRoNs w|LL|AM R.MARsHALL,JR., BY GEORGE w. MURRAY, J2,

HENRY RAlcH.

AGENT Aug. 23, 1960 E. l.. ARMSTRONG ETAL 2,950'249 GREASE-MAKING PROCESS INVOLVING MECHANICAL ATOMIZATION Filed Sept. 13, 195'? Y 5 Sheets-Sheet 3 L0 8 ci 8 Ll. 2 f2 E s 1"- 8 C o GD D O n 2/ o s t0 o O 0 TIME SECONDS sooo 4o :o

O D Q o o o ro o o o o A .n 8 8 A o iv U) f o N O O QJ JQ E E 8 n Q D INVENTOR. Q ELDoN L ARMsTRoNG O wu |AM R.MARsHALL,JR.,

l BY GEORGE w. MURRAY, .J l2, l HENRY RAlcH.

AGENT Aug. 23', 1960 E. ARMSTRONG Erm.

GREASE-MAKING PROCESS INVOLVING MECHANICAL ATOMIZATION 5 Sheets-Sheet 4 Filed Sept. l5, 195'? AGENT Aug. 23, 1960 E. 1 ARMSTRONG ETAL 2,950,249

GREASE-MAKING PROCESS INVOLVING MECHANICAL ATOMIZATION Filed Sept. 13, 195'? 5 Sheets-Sheet 5 B i. L

Gross Piece 84 85 Chamber Gagset 'Pinile 85 87 Orifice 83 F I G. 8

40 Threcds/ inch ITurn=0,025"

F I G. iO

87 Vernier on Foce 125 Divisions lDivision= og 0.ool'

INVENTORS.' Ve'fc MONO" ELDoN L. ARMSTRONG,

WILLIAM R.MARsHALL,JR., By GEORGE WMURRAY, Jia] HENRY RAlcH.

fpm. QW-

AGENT GREASE-MAKING PROCESS INVOLVING MECHANICAL ATOMIZATION Eldon L. Armstrong, Garden City, N.Y., William R. Marshall, Jr., Madison, Wis., and George W. Murray, lr., Pleasantville, and Henry Raich, East Meadow, N .Y., assignors to Socony Mobil Oil Company, Inc., a corporation of New York Filed Sept. 13, 1957, Ser. No. 683,815

13 Claims. (C1. 25232) This invention relates to the art of grease manufacture and, more specifically, has to do with a multi-stage mechanical atomization of grease-forming materials to produce a grease.

Armstrong, Butcosk and Murray have described, in application Serial No. 458,158, led September 24, 1954 (which has been abandoned), and more recently, in continuation-in-part application Serial No. 682,461, filed September 6, 1957, methods for manufacturing grease. The methods are of the following nature. A mixture of an oleaginous vehicle and soap-forming material is constituted. A soap is formed in situ in the vehicle. The resulting vehicle-soap mixture, at a temperature below its solution temperature, is subjected to mechanical atomization into dispersed droplets. The latter are instantaneously contacted directly with a substantially cooler surrounding atmosphere to effect heat exchange thereof. In this way, a grease is formed.

As generally understood, and as pointed out in the latter application, solution temperature is that temperature at which substantially complete solution of a soap thickening agent in the liquid lubricant occurs. Thus, it is that temperature at which the soap thickening agent is present as discrete molecules or at most molecular aggregates (crystal nuclei) approximately colloidal dimension in size. As a further expression, it is that temperature at which the Tyndall beam disappears in the mixture.

While each grease is characterized by a solution temperature, it isV also often characterized by one or more transition temperatures. That is, a soap can exist in different crystalline structures while the soap is in the solid state, insoluble in the oil portion. These crystalline structures differ in degree of crystalline order and degree of interpenetration of oleaginous vehicle with the soap crystalline structure. stable over a denite but limited temperature range. Thus, the temperature at which a change occurs in the crystalline structure of the soap portion of a grease, is a transition temperature. lt may also be regarded as a temperature at which a phase change occurs in the grease. Such a temperature is less than the alreadydened solution temperature.

While the procedures described in the aforesaid Armstrong et al. applications constitute substantial steps forward in the art of manufacturing greases, it has been found that greater control in producing greases of desired characteristics can be achieved in a related but distinct operation. Thus, greater control over yield, consistency, mechanical stability, texture and the like, are made possible by the new operation. As understood in the art, yield is the amount of grease of a given consistency which may be made with a definite amount of thickening agent. As the yield increases, the percent of thickener decreases. Consistency, or hardness, refers to the degree to which a plastic material such as lubricating grease Each crystalline soap structure is Patent resists deformation under the application of force. Thus, it is a characteristic of fluidity. It is usually indicated by either apparent viscosity or ASTM penetration. Mechanical stability denotes the resistance to change in consistency when a grease is mechanically worked or sheared; further, it is generally measured by such tests as the Shell Roll Stability Test and the Motor Matic Worker Test. Texture, as it is commonly referred to in the art, denotes, the structural appearance of a grease, for example, smoothness, brosity, stringiness, etc.

In addition, in the new operation, it has been possible to effect substantial economies in the preparation of commercial quantities of greases, over prior art procedures including those of Armstrong et al. indicated above. For example, we have found that with a lithium-calcium soap grease, as defined hereinafter, twenty to thirty percent less soap-forming ingredients need be used in the new procedure than in the aforesaid procedures of the Armstrong et al. applications, in order to obtain a grease of comparable consistency and mechanical stability.

The new operation comprises: constituting a mixture of an oleaginous vehicle and soap-forming material; forming a soap in situ in the vehicle, at a temperature above, at or below its solution temperature, such that a minor quantity of water is present therewith; subjecting the resulting vehicle-wet soap mixture, at a temperature below its solution temperature, to mechanical atomization to form dispersed droplets and instantaneously contacting the droplets directly with a surrounding atmosphere, whereupon the vehicle-wet soap mixture is substantially dehydrated; and thereafter subjecting the substantially dehydrated product, at a temperature below its solution temperature, to a more intense mechanical atomization to form dispersed droplets, whereupon homogenization is obtained, and instantaneously contacting the said droplets directly with a substantially cooler surround- .ing atmosphere to effect heat exchange thereof. All of the oleaginous vehicle can be added initially in constituting the mixture of vehicle and soap-forming material or part only of the vehicle can be so added. In the latter practice, the remainder of the Vehicle or vehicles can be added following the dehydration step, or following atomization of the substantially dehydrated product, or portions of the remainder of the vehicle or vehicles can be added after each of these steps. It is to be understood also that an additive or additives can be added at any one or more of such stages of the manufacture.

Accordingly, the primary object of the present invention is to provide an improved grease manufacturing operation whereby the properties of a grease can be controlled more readily during manufacture.

Another object is to provide a grease manufacturing operation whereby imrpoved yield is obtained.

Still other objects are to provide a grease manufacturing operation wherein control of mechanical stability, texture and/or color can be achieved.

Another object of the invention is to provide a rapid grease manufacturing operation.

Another object is to effect economies in grease manufacture.

Still other objects will be apparent from the following description.

In order that the invention can be readily understood, reference is now directed to the drawings which are attached to and form a part of this specification.

In these drawings, t

Figure l is a highly-diagrammatic form of a typica system for practising the invention.

Figures 2 and 3 shows, respectively, a vertical section and a horizontal section of a low pressure atomizing Patented Aug. as, raso Vanalysis curves of individual greases. Vmal analysis isdescribedfby D. B; CoxandJ. F. McGlynn Figures v8 3 nozzle of a type useful in the practice of the invention. Figure 4 shows a cross-section of a high pressure atomizing nozzle suitable for use herein.

Figures 5 and 6 show Vtypical differential thermal Differential therin AnalyticalV Chemistry, .volume 29, Pages 960963, Iune'1957. 1

f, Figure I7 Vshows Vthe'efie'ct of shearirate in 'the initial mechanical atomization operation upon certain' representative characteristics of an individual grease, a lithium soap grease .containing a minor proportion of calcium soap.

and 9 show, respectively, a vertical and -a horizontal cross-section of 'a pintle valve, Vpressure atomizing nozzle useful in investigating the lects of shear rate Von a grease in the dehydration-atomization step. Figure 10 indicates the dimensions in theoriiice region of a particularpintle valve, pressure atomizing nozzle used for theY above purpose; I Y

' rReferringto'Figure l, 1Q is a contactor such as for example the Stratco-'contactorf'supplied by the Stratford Engineering Company and well known in the art, in which adequate mixing of charge Vmaterials accompanies heating. It ispto be understood that a pressure kettle, autoclave, etcl can be used in place,l of a Stratco contacter, but Ithe latter is preferred. YLine 11 is a charge line for introducing ingredients to contactor 10. Heat is supplied to 10 bycirculating Vhot oil, stream or the like through line 12 and the jacket 13thereof. Part or all of the constituents expected to be present in the nished grease are chargedfthrough line 11. These constituents will be oleaginous material, such as mineral oil, the thickening agent'components, and additives, such as antioxidants and the like. forming ingredients, which can be acids including fatty acids and lower molecular weight acids, glycerides and the like, and appropriate metal compounds such as lime flour, sodium hydroxide, lithium hydroxide, and the like, are so added. VIt is .essential that the soap-forming materials so charged provide arminor Vquantity of water. The `Water,..as determined by Karl vFischer titration, should be atleast Vabout 0.25 percent and not more than Vabout 2O1percent,.and preferablyat least about 0.5 per- Y cent lor, more but not more than about 10 perccent, when lthe ingredients react to form a soap or soaps in con- Vtactor 10; or a quantity Vof water s'hould be charged through line'i Vto provide such an ultimate water content in the. mixture taken from the bottom of 10 throu-gh discharge line 1d. In 10 the ingredients are heated, under a superatmospheric pressure ofthe orderof 100 p.s.i. or at leastV suicient to preventescape of volatile constituents or'reaction productsfto a temperature and for a time suiijcient to ensure completion of any desired reaction, such as neutralization orV saponication. VThis temperature will ordinarily be -of the orderof Z50-400 F., as explained in greater detail hereinafter. However, kthe temperature of the 'heated mixture can be maintained at,

Vabove or below its solution temperature.

gas pressure should be at least sulicient for the atomization required in nozzles 20; Spray manifold 18, for example, can comprise a 2 inch pipe'havingffour 1/z'inch pipes'19.V Each ofV lines v19 is equipped with a low pressureatomizing nozzle 20. The temperature ofthe productgas itreaches nozzles 20vis below its'solution temperature.

The mixture in lines -19 passes through nozzles 20 into receiver 21 such as a typical grease kettle equipped with a motor-driven agitator 22. As shown, the temperature of the Ymaterial in 21 can be regulated by oil, steam or the like circulating through line 23 and jacket 24. Finely dispersed droplets emerge from nozzles 20 into receiver 21 and are contacted with-a surrounding atmosphere in 2i), itis substantially dehydrated.

The thickening agent components or soap-V receiver 21. As the material emerges from the nozzles IIn general, a water content of less thanV about 0.25 percent by weight is desired. This applies to substantially all greases; however, With a few grease types,V such as calcium cup greases, ythe Water content should be maintained 4at a level ofy aboutjone percentby'weight of water in order that structure stability be maintained. The. water dashed from the product escapes through duct 25. `Part of this water may condense'to droplets of liquid water. Air admitted to receiver -21 through `inlets26 surrounding lines 19 sweeps out (through'ZS) a mixture of Water vapor` and water droplets. I 'I Receiver 21 shouldl havefa capacity ofat least about 11/2 times the volume of the material delivered from contactor 10 to allow for aeration, in the event the dehydrated productr isretainedV in 2.1 before being further processed as described hereinafter. Y

Sufiicient air is supplied through inlets 26 surrounding lines 19 carrying nozzles 2i) to sweep out water vapor and wet droplets. If dehydration alone is desired in the .initial atomization, Ythe quantity of air need not be sufficient to carry off all of the Water flashed oi as water vapor, sincemuch of the water can be carried on as water droplets. This .reduces the air demands for dehydration and also minimizes cooling of theV sprayed product. It has been noted that wet product delivered to nozzles 20 is cooled approximately 18 F. for each one percent of water removed by dashing o yinto Water'vapor during atomization, because the latent heat of Vaporization of the water removed is supplied by the hot product. Further cooling of the sprayed product due to heat transfer of sensible heat to the air used to sweepy out water vapor and water droplets, Will also occur. Of course, should additional coolingof the sprayed product beidesired the quantity of air delivered through inlets 26 can be increased. p

In the event a soap concentrate is prepared in YMtv/ith only part of the entire oleaginous vehicle, instead of a mixture with all of the vehicle, all or part of` the re-` mainder of the vehicle or vehicles can beV 'added to receiver2'1 through line 27. it is to be understood that one or more additives can also be charged, iin part or in entirety, through line 27.V

. The product in receiver 21, maintained below its solution temperature, is removedthrough valved line 2S by pump V29 and is Vdischarged into valved line 3i). If desired, the product Vcan be recycled through valved line 31 for return to receiver 21. This is desirable in order to partially deaerate the product in receiver 21 to reduce its total volume, and/or to aid in mixing-'the product andrany additive or additional vehicle charged Vthrough line 27. As shown, the product can also be recycled to Wnozzles 20 by way of lines 31, 32, 13 and 19. This is advantageous when ythe water content of the product has not been brought to -the desired low value in a single pass throughnozzles 20. n

Generally, product in line 30 is passed through pump 33, preferably of high pressure positive displacement type, and is discharged therefrom ,through'line 34 to spray manifold 35. VThe latter (35) is equipped with one or more lines 36 terminating in vone or more atomizing nozzles 37. Here too, the temperature of the-product in line 2S through to nozzles 37 is Vso maintained as to be below its solution temperature. Y

Finely dispersed droplets emerging from'nozzlesr37 are Y collected in receiver 38.3 Asshown, receiver 38 is aconventional grease kettle equipped with a motor-driven paddle-type agitator 39. In general, it is preferred that the agitator 39 be activated from the bottom of receiver 38, as shown, rather than of the type represented by agitator 22 in receiver 21; in this way, the top of receiver 38 is left free for better arrangement of atomizing nozzles 37, air inlets and outlet ducts. Temperature of receiver 38 can be regulated, as with receiver 21, by circulating hot oil, steam, etc. through line 40 and jacket 41. Air or other gas is brought into 38 through inlets 42 and leaves through outlet or exhaust duct 43. Air serves as the cooling atmosphere for instantaneous Contact with dispersed droplets formed by atomization in order to eect heat exchange by convection. The air also serves to sweep out of receiver 38 any additional wet droplets and water vapor flashed from the atomized product discharged from nozzles 37. Generally, from about 0.5 `to about l pounds of air are added through inlets 42 per pound of product; preferably, from about 1 to about 4 pounds of air per pound of product are so added. As the product is discharged from nozzles 37 into receiver 38, it is subiected to mechanical atomization into dispersed droplets and the latter are cooled virtually instantaneously by convection heat exchange with the substantially cooler surrounding atmosphere maintained in 3S, and particularly the atmosphere immediately adjacent nozzles 37. Some cooling may also be obtained by virtue of the latent heat of vaporization supplied by the material charged to nozzles 37, in vaporizing any additional water and/or other volatile material, released on atomization, since additional dehydration can occur in this atomization.

In receiver 38, it is desired that there be intimate and prolonged mixing of the droplets (from 37) with the air therein. Eifective cooling of the product in receiver 38 has been realized by using ducts 44 at air inlets 42, such that incoming air travels down for a substantial distance with the dispersed droplets in a confined volume before it can reach the air exhaust duct 43 entrance. By using such air inlet ducts 44, it is possible to obtain a relatively high velocity of the entering air to achieve more intimate and prolonged mixing of the air with the dispersed droplets from nozzles 37. It is preferable to so place the entrance of exhaust duct 43 to maintain longer contact of incomingl air from 44 with the dispersed droplets from nozzles 37 before the air is exhausted from receiver 38. It Vis also preferable that the entrance of duct 43 be of relatively large cross-sectional area, in order that carry-over of fine droplets of atomized material be minimized or avoided. lt is to be understood that design and location of the air flow system, with relation to the location of the nozzles, can be varied considerably with the objective of making eicient use of the incoming air without undue loss of product by carry over of ne A droplets.

lt is to be understood that other atmospheres than air introduced through inlets Z5 and 42, can be used. For example, nitrogen, carbon dioxide, iiue gas, steam and the like can be used.

The product collected in receiver 38 has a grease structure and is generally highly aerated. It is removed from 38 through valved line 45 by pump 46, and is passed through pipe 47 to deaeration in deaerator 48. The latter can be any of those usual in the art, such as a Morehouse deaerator, a Cornell code grease homogenizer, a Kinney Heli-Quad vacuum pump, or of the type described by Brooke and Piazza in U.S. Patent No. 2,797,767. These devices generally operate on a vacuum principle. Grease emergent from deaerator 4S through line 49 can be pumped by pump 50 and line 51 through a conventional filter 52. The linished grease is taken through line 53 and is packaged in equipment designated 54.

Grease in line 47 can also be recycled for further atomization in nozzles 37, by return through line S5' to line 30. This is desirable in order to obtain additional homogenization and/or cooling, if such is needed.

Any remaining vehicle or vehicles or additives required can be charged to receiver 38 through valved line 56. As a further modification, grease in line 47 can also be recycled to receiver 38 via valved lines 57 and 56; this is advantageous to aid in mixing vehicle or additive charged through line 56 with product collected in receiver 38. It is also advantageous in removing some of the entrapped air in the product collected in receiver 38 prior to deaeration in 48.

Line 5S, in line 34, is provided as a pressure release line for safety purposes.

Figure 2 of the drawings shows, a vertical section, taken along line B-B (see Figure 3), of a typical low pressure atomizing nozzle found useful for the initial mechanical atomization to effect dehydration. The nozzle is composed of a body 6@ containing an inlet passage 61, which enters tangentially swirl chamber 62 so that the material passing into chamber 62 has a vortical motion. Here, material swirls around and down, acquiring increasing tangential velocity components. Below the swirl chamber, replaceable orice cap 63 is secured to body 66 as shown. Material issues from the oriiice as a hollow conical sheet which atomizes into a so-called hollow-cone spray. The diameter of a typical oriiice cap 63 useful herein is 0.36 inch. This nozzle is supplied by Spraying Systems Company, as 1/2 B-40 whirljet nozzle. 'Ihroughput characteristics of the nozzle can be regulated by varying the nozzle body size which alters the entrance diameter (of inlet passage 61) and swirl chamber (62) sizes, and by varying the orice diameter which can be changed independently by substituting orifice caps with dierent orifice diameters. Varying the feed pressure to the nozzle also varies throughput.

Figure 3 is a horizontal section of nozzle 20, taken along the line A-A (see Figure 2).

F1gure 4 reveals, in cross-section, a typical high pressure atomizing nozzle found effective for the second and more intense mechanical atomization to effect homogenilzatlon and cooling. This is composed of body '70 containing ow path 71. Toward the end of ow path 71 there 1s a removable core 72, of hexagonal or square crossesection, and having grooves 73. The core is held in place by orifice cap 74 which is secured to body 70 at shown. As material flows through path 7l, it passes along core 72 through annular passage 75 defined by core 72 and cap 74. Material is expelled through orice 76 of cap '74. The material acquires tangential velocity components in passmg through the grooves 73 in core 72. This causes the stream of material to exit from orifice 76 as a hollow cone which atomizes into a hollow-cone spray. In general, the spray emergent from such a nozzle is ner than from the nozzle illustrated by Figures 2 and 3. This litting of Figure 4 is of heavy construction, being designed for pressures in passage 75 of several thousands of pounds per square inch. The dimensions of one grooved-core nozzle found useful were: oritice diameter, 0.134 inch; a slx-grooved core, each groove cross-section being 0.050 by 0.065 inch. Such a nozzle is supplied by Spraying Systems Company, and is identified as 1/2 SB 30 nozzle, number 40 core.

In place of the atomizing devices illustrated by Figures 2, 3 and 4, other such devices known in the art cany be used. For example, the following can be mentioned: impinging jet nozzles, centrifugal or rotating disc atomizers, pneumatic atomizers, vibrating atomizers, multi jet atomizers, impact type nozzles and other liquid dispersing devices.

Salient features of lthis invention are described below in connection with several typical, and non-limiting, examples. In this description, the same grease-composition defined in Example 1 was used unless otherwise indicated.

of this grease.

7 AroMrzATroN CONDITIONS K Y Example 1 This' involves the preparation'of a lithium-soap grease containing a minor amount of a calcium soap. The grease was prepared from the following materials: i

Formula: y Weight percent Palmitic acid 0.49 Stearic acid 6.30 Oleic acid 0.21 Lithium hydroxide monohydrate 0.848 Lime ilour- 0.368 Oxidation inhibitora 0.2 Multipurpose inhibitorb 2.0 Naphthenic mineral oil, 750 secs. S.U.S. at.100 F 58.23 Naphthenic mineral oil, 135 secs. S.U.S.

'atZlO F 1.354

aThis is aV mixture of mono and diheptyl diphenylamines.

bThis is an `oil blend containing; part (by weight) of`il and one part of a reaction product obtained by reaction of naphthenic acid and diethylene triamine and isrdescribed in application Serial No. 683,681, led September 13, 1957.

This grease has a solution temperature of about 376 F. The soapV portion of the grease'can Vexist in three different crystalline structures while the soap is in the solid state, insoluble in the oil portion. Each crystalline soap struc- -ture is stable `only over a limited but deiinite temperature range.V On heating from room temperature, the stable soap structure present at the latter temperature persists until the temperature of the grease reaches approximately 305 F. At this temperature, with continued heating the soap changes to a second crystalline structure which persists to about 347 F. Here the soap portion undergoes another change in crystalline structure which is stable up to about ,376 F. Above 376 F., the solution temperature, the soap dissolves in the oil. All of this is shown by Figure 5, a differential thermal analysis curve The peaks shown in the curve mark the transition temperatures or phase transitions.

Now With regard to preparation of this grease Vand with reference to Figure l, all of theingredients shown were charged through line 11 to a vertical Stratco contactor 10. The ingredients, totallingel0,000 pounds, occupied about 90 percent of the volume of the'contactor. It has been found that moreV advantageous operation often results when the charge to contactor Volume ratioy is high. The Stratco was heated with circulating hotoil. Throughout the preparation, the temperature of the hot oil entering the Stratco jacket was maintained betweenY 280 F.-295 F. At the time charging .of the Stratco had been completed, the temperature of the mixture of ingredients was about 160 F. The ingredients were heated to about 270 F. in about 75 minutes. The ingredients were maintained at 270-280 F. for about 25 minutes until saponiiication was complete; at this point, the pressure in contactor was about 40 p.s.i; Completion was determined by sampling the material in the contactor and agitating it with a few drops of a phenolphthalein solution.AY The indicator turned pink (alkaline reaction) when saponication was complete.

The ingredients. yielded on saponiiication a quantity or" water, formed by reaction plus water of hydration of the lithiumV hydroxide monohydrate charged, Yamounting to `about 0.81 percent by weight of the total charge in con- Y tactorlo.

contactor while the contents thereof were discharged.

The material in contactor 10 was discharged by the air pressure in the head spacein contactorY 10, to spray -rnanifold 18,;and thence to four nozzles 20. Before entering the nozzles, the temperature of the materialrwas below .2807'.5-...1'1152 .nozzles were gf the typeshcwnhy A Figures Zand 3, kand each had an oriiice diameter of 0.36 inch. The temperature of the material collected in receiver 21 was 264P F. The dispersed droplets of atomized material were contacted instantaneously with a Ysurrounding air atmosphere and were then collectedand agitatedin grease kettle 21, `a 20,000 pound capacity kettle, jacketed, and having rotating paddles. The atomizedY material had a water content of less than0.25 percent by weight. Water removed during atomization was exhausted as'water vapor and Water dropletsthrough duct 25, by sweeping out the same with air admitted to receiver 21 through inlets 26. V

Following collection of all of the atomized material in kettle 21, it was discharged by pump 29 through lines 28 and 30 to a high pressure pump 33. It was discharged from the latter at a pressure of 1600-1800 p.s.i. and at a rate of about 10,000 pounds per hour, to line 34 and thence to four nozzles 3'1'7.` The'` nozzles were of the type described above in connection with Figure 4. The temperature of the material before Apassage through nozzles 37 was 244YF. As the material was atomized by nozzles 37 into receiver 38 it was homogenized and cooled. Cooling was eifected primarily by contact with air brought into 38 through inlets 42 at a temperature of 85-90 F. and at `a rate of about 2.2 pounds of air per pound of material being atomized. Air was removed from 38 through exhaust duct 43. The air temperature in exhaust duct 43 was 153 F. as compared with its inlet tempera- .ture of -90 F. The `dispersed droplets of product from nozzles 37,V after collectionin receiver 38, were at a temperature of 171 F. following contact with the cooling air.

The grease collected in 38 was then deaerated and filtered as described above. It had the following physical properties: A

PHYSICAL PROPERTIES OF FINISHED GREASE' ASTM penetration:

Unworked 282 Worked, 60X, 1A" holes 287 Worked, 10,000X, 1A" holes 324 Rolling stability-Z hours:

Micro penetration, initial Micro penetration, iinal Y Texture ySmooth Wheel bearing leakage, 90 gram pack, grams 1.5 Water content, percent (KarlFischer method) 0.10

Example 2 This example involves the preparation of lithium soap greases having the composition described in Example l. In this example, however, the effect of operating conditions in the initial atomization is demonstrated.

Referring to Example l and the product taken from contacter 10 through line 14 to nozzles 20, it has been found that this wet saponiiied product can be broken 'down by excessive shear during atomization. In order to dehydrate this material, suitable `atomization conditions must be maintained. Excessively iine -atomization in dehydrating the wet material leads Vto a product which at this -thickenei' content is soft (low yield) and has less mechanical stability.v Correspondingly, too coarse atomization leads to incomplete dehydration of the wet material, which again leads to a product which issoft (low Yyield) and haslessA mechanical stability. V"i'hus,the initial atomization should be eected under conditions sufficient to eiect properdehydration and yet not so severe as to produce excessive breakdown or" the product.

Emciency of dehydration and breakdown of the wet saponied product are aected in opposite directions by varying the shear rate in spray nozzles. Efficiency of dehydration increases rapidly with increasing shear rate (conseqently finer atomization) in the nozzles. Increasing shear rate during atomization also increases the extent of breakdown of the atomized product. As a result, it is possible to select nozzles and atomizing conditions which give a proper balance of desired results, including dehydration, mechanical stability and yield. This is illustrated by Figure 7. Data on which Figure 7 is based was obtained by using a pintle valve nozzle (shown by Figures 8, 9, and 10, described below) in which average shear rates could be estimated. Batches of this grease having the same formulation as in Example l, were saponitied under the same conditions as detailed below:

Charge, total weight, pounds 100 Charge saponication temperature, F. 288-298 Stratco hot oil temperature, F. 285-295 Saponication total time, minutes 41-53 Water content of charge before atomization,

percent wt. 0.81

Air pressure applied to Stratco before charge is atomized, p.s.i 100-110 Each batch was spray dehydrated at 100-100 p.s.i through this pintle valve nozzle. The clearance in the orifice of the nozzle (consequently the shear rate) was varied for each batch. After spray dehydration each batch was spray cooled and homogenized by atomizing through a high pressure nozzle of the type shown by Figure 4, the same nozzle and pressure being used for each batch. Each batch was then deaerated. Each batch Was sampled during the various stages of the process.

Figure 7 shows the ASTM penetration of the nished deaerated grease to be a minimum (maximum yield) at a shear rate during the initial atomization of about 35,000 second '-1. Similarly, the rolling stability both immediately after spray dehydration and after finishing, is ya maximum (minimum micropenetration after rolling) at about the same shear rate. The data show that the properties of finished grease can be controlled by proper selection ofthe atomizing conditions during the initial atomization. For example, the data indicate the need for a shear rate of at least about 20,000 and not greater than about 80,000 reciprocal seconds in the initial atomization to produce this grease having optimum balance of yield and mechanical stability. Maximum yield and mechanical stability are realized with shear rates from about 30,000 to about 50,000 reciprocal seconds in the initial atomization for this particular grease formulation.

The pintle valve mentioned above in connection with Figure 7 is shown in Figures 8, 9 and 10. Figure 8 is vertical section of the pintle valve, taken along line A--A (see Figure 9). This valve is composed of body 80, having a iiow inlet 81, and to this body Si) is attached a chamber piece 32, having at its outer end an orice S3. The upper end of chamber piece 82 has a cross member 84 lin which there is a threaded passage S5. Threaded pintle 86 screws into this passage 85, so that its conical end 87 may be adjusted with respect to orice S3 to give a spray orice of desired character and give rise to a spray having generally the characteristics of a hollow cone,- but without tangential velocity components. Gasket 88 is provided between chamber piece 82 and body 80.

Figure 9 is a horizontal cross-section, taken along the line B-B, of the nozzle shown in Figure 8. l

Figure l shows the dimensions in the oriiice region of a particular pintle valve nozzle suitable for investigating shear rate eects. Shear rates obtained with this pintle valve nozzle were estimated in the following Way. Maximum shear was assumed to occur in the annular orifice 83. Therefore, the shear rate was dened as the average velocity in the annular oritice divided by the average width of the annulus. The distance l was made sufficiently short such that the velocity variation in the annulus was small. The velocity was estimated from the flow rate and orifice area, and the annulus width was determined from the angle of the orice wall, the length l, and the position of the pintle valve which was adjusted by means of carefully machined threads. The area of the annulus was calculated from the geometry of the nozzle and the position of the pintle valve.

Atomizing devices found suitable for the initial atomization also include a nozzle of the type shown by Figures 2 and 3 wherein the orice diameter was 0.36 inch and the wet saponiiied product fed to the nozzle was under a pressure of about p.s.i. For a grease composition whose Wet soap following saponication is susceptible to substantial breakdown when sheared excessively, the properties of the final composition can be controlled by the .shear rates employed in the atomizing devices of the initial and subsequent atomizations. In the initial atomization of a lithium-calcium grease of the type shown here, the shear rate will be within a range corresponding to the range of about 20,000 to about 80,000, and pref-A erably about 30,000 to about 50,000 reciprocal seconds as determined by operation of the pintle nozzle described above. In other types of atomizing devices employed in the first atomization, such as nozzles shown in Figures 2 and 3, the device design and operating conditions are such as to result in shear on passage of the wet soap mixture therethrough as to correspond to the above-mentioned shear rate ranges defined with the pintle nozzle. In any event, the atomization in the second or subsequent atomization of such greases is more intense than that employed in the initial or prior atomization.

SECOND-STAGE ATOMIZATION Example 3 This example reveals the eect of operating conditions in the subsequent atomization. Again, the grease was that described in Example 1.

In this example operating conditions during saponitication and the tirst atomization stage were the same. The nozzle used had an orice diameter of 0.36 inch, and the pressure was 100 p.s.i. Two 100'pound batches were prepared. Batch A was subsequently atomized at a pressure of p.s.i. through a low pressure spray nozzle of the type shown in Figures 2 and 3, having an orice diameter of 0.22 inch. Batch B was subsequently atomized at a pressure of 1800 p.s.i. through a high pressure spray nozzle of the type shown in Figure 4, having a corel containing four grooves, each groove 0.020 by 0.35 inch in cross-section and an oriiice with a diameter of 0.051 inch. Both batches were sampled after the second stage atomization, during which cooling and homogenization were obtained.

The ASTM unworked penetration of batch A was 315, and of batch B was 276. This dierence is an indication of the leakage which might be encountered in 1ubricating ball bearings of vertical motors. Batch A with a value of 315 would have poor sealing properties; whereas, batch B with a value of 276 would stay in place.

Atomization by spray nozzles in the second-stage atomization is an effective means of homogenizing grease. Homogenization occurs during atomization because the grease is sheared during tlow through the nozzle. A further source of shear is the mechanical disintegration of the conical sheet of grease issuing from the nozzle into droplets. These two effects cannot be separated readily, but most probably the principal effect is shear during flow in the nozzle. High pressure atomization is more effective for homogenizing than low pressure Y atomization in the second stage, probably because the velocities (and consequently the shear rates) in high pressure nozzles are much higher.

. 11' TEMPERATURE The temperature reached during saponiiication is an important factor aie'cting the subsequent processing required to produce a finished grease. 'The saponitication temperature determines the phase of the soap thickener after saponiiication Vis completed. This, in turn, determinesV the processing required after dehydration of the wet soap to permit the soap to go through necessary phase transitions, if any, before reaching itsY phase structure stable at room temperature (about 70 FL).

Transition temperatures vof the grease dened in Example 1 have been described above. It has been noted that transition temperatures are only slightly affected by soap concentration in the ranges of soap content normally used in grease manufacture, that is, 3 to 50 percentby weight, i

The transition temperatures reported above were obtained by slow heating. However, if the grease were 'cooled from above 376 F. where the soap is soluble inthe oil, the phase transitions found would generally occur at lower temperatures than those found on heating. This is due to supercooling. The amount of supercooling can be very large, Amore Ythan 50 F. for some phase transitions, depending on the Vcooling rate and degree of agitation during cooling. Supercooling is minimized by slow cooling andV rapid agitation.Y

Grease manufacture is concerned with the'existence and rates of phase transitions because soap base greases arerconventionally prepared at high temperatures, usually above the solution temperature. Subsequent processing then involves slow, controlled cooling and working in kettles. During the cooling and working 4cycles the soap crystallizes out of the oil and undergoes the various phase transitions, if any, characteristic of the system before reaching the soap structure stable at room temperature. Careful control of the cooling cycle is needed to insure minimum supercooling and maximum completion of the phase transitions as well as growth of the desired fibre structure of the soap inV the oil.

KnowledgeV of phase transitions is important in applying atomizing techniques tov grease-making, primarily because of the speed of cooling obtainable by atomization. Consider the subsequent atomization stage in which cooling and homogenization result. VThe soap thickener'in the productbeing fed to the atomizing device should be inthe desired phase stable at room temperature for maximum yield and mechanical lstability to beobtained. This is necessary in the second stage because the product passing through the atomizing device is rst homogenized by shearing in the Vatomizing device and then the dispersed droplets are virtually instantaneously cooled through a substantial temperature drop when atomized into a cooler air stream. If the soap thickener were in a phase not stable at room temperature when fed to the atomizing'device, this phase structure would be highly supercooled andsubsequent transition to the phase stable at room temperature would occur only partially,if at all, depending onthe rate of transition between these two phases.` v is Y It is advisable to consider not only theV temperature ofthe mass being processed but-also the temperature of the heating medium 12. For example, in a yStratco Ycontacter heated by a hotoil `circulatingthrough the jacket 13'thereof, it is advantageous-to control .the temperature of the oil lest the temperature greatly exceed the temperature desired for the grease mass within the contacter. In conventional practice, the heating` medium (hot oil or huid) in the contacter `jacket. is maintained considerably higher in temperature than the bulk temperature'of the reactants in order to Yobtain as large'a temperature differential as Vpracticalsothatreasonable heat transfer rates are-realized- YSin'cethe Vreactant mixture'is a relatively good. .thermal ninsulator, in fconventional- -practice vthe Afilm .temperature ofk the mixture in contact with Ytheheat transfer, surface is convdiscussed above.

Y 12 siderably hotter than the bulk of the mixture. This hot lm is continuously beingrworked back into the mass by vigorous agitation in the vcontactor and cooled by the mass. `The hot film is replaced by cooler material from the mass. Under conditions where the heating medium `is WellV above a transition temperature and the bulk of the mixture is below it, the lm temperature of the mixture in contact with the heat transfer surface can exceed its corresponding transition temperature. The soap in the flmwill then undergo a phase transition to a phase stable at the corresponding higher temperature of the film andv will then be mixed back into the cooler bulkV material. 'If the material previously in the tilm is suciently supercooled when mixed back into the mass, or if the rate of phase transition back to the phase stable at the lower temperature of the mass is slow, the soap in this portion of material previously in the film will remain at least partially in the higher temperature phase. It is, therefore, possible, under normal processing conditions, to transform part of the soap inthe mass being heated into a phase which is supercooled and unstable at the temperature of the mass. 4

Y Y. Example4 V This example is provided to demonstrate that the properties of greases obtained in the present invention can be controlled by proper regulation of operating Yternperatures. Again, the grease deiined lin-terrn's of its composition in Example 1 was used.

In batch A, the saponiiication temperature andthe temperature of the Stratco Vheating medium were below `the lowest transition temperature of 305 F. Batch B was prepared under conditions such that the bulk of the saponication mixture in the contactor was below this transition temperature (305 F.), and the heating medium was substantially above such temperature. The operating conditions and the physical properties of the grease products obtained in each preparation are tabulated below:

v l s A Y B Saponitlcatiou Conditions: Y

Charge Weight iu Pounds 10D 100 Bull; Temperature of Saponieation Mixture,

F 29S 296 Y Heating Medium Temperature, 9F 29o-300 390-350 Dehydration Conditions:

ressure at Nozzle, p.s.i. (Figs. 2-3)- V 102 105 Temperature after Atorrdzation, "F V 30O Y 300 Second Stage Atomization:

Temperature before Atomjzation, F 261 265 Pressure at Nozzle, p.s.i. (Figs. 243) 150 Temperature after Atomization 170 Properties of Deaerated Products:

ASTM Penetration- Unworked 29,0 345 Worked, 60X, }/4" Holes 304 363 Worked, 10,000X, 54" Holes 341 Rolling Stability, 2 Hours- Micro Penetration, Initial 112 158 Micro Penetration, Final 174 282 Batch B illustratesthe influence of film temperature While the bulk temperature during the saponcation remained below 305 F., the heating medium temperature was such that nlm temperature duringV saponication exceeded 305 F. The product of batchvB shows lower yield, yand lower mechanical stability than did the product of batch A, Where both the bulk temperaturenand the heating medium temperature remained below'305 F.

It is to be understood that the greases of batches A and B are Vsatisfactory products, thoughV theysdiier in `their nal characteristics,y and though batch A has Athe better yield and mechanical stabilityrof the two products.

Thus, the control of` temperature provides a means for controlling-the properties desired in a grease product.

` Y l Y Example 5 The, importance of control oflm'temperature during processing subsequent to sapbnication 'and the initial 13 atomization step is illustrated by the following data. This batch was prepared under the same conditions and with the same quantities as those used in Example l. The bulk temperature and heating medium temperature during saponication, and the atomization temperatures, were all below 305 F. A small portion of the batch in receiver 38 at a temperature of 130 F. was deaerated. The bulk temperature of the remainder'in receiver 3S was then heated to 180 F. by passing steam at 100 p.s.i. (about 335 F.) through the jacket 41 of receiver 38. This material was then deaerated. Properties of the portion deaerated at 130 F. and of the portion after heating to 180 F. are shown below:

In this preparation, as in Example 1, above, receiver 38 was a 20,000 pound capacity kettle, jacketed, and having rotating paddles but no Scrapers. With such a receiver, the film temperature is substantially the same as the temperature of the heating medium in the receiver jacket. The lm temperature, then, exceeded the lower transition temperature of 305 F., although the bulk temperature did not exceed 180 F. The etects of ex'- ceeding the transition temperature are evident from the tabulation given above. That is, the yield of the product was reduced by exceeding the transition temperature in the film.

Example 6 An additional example of the preparation of the lithium-calcium grease of Example 1 is set forth below.

Naphthenic mineral oil, 750 secs. S.U.S. at

100 F. 90.997 Water 1.0

The ingredients were charged to a Stratco contactor. Saponiiication was carried out up to a temperature of 292 F. Pressure in the contactor was 51 p.s.i. The saponication mixture was then atomized through a nozzle of the type shown by Figures 2 and 3, the nozzle having an orifice diameter of 0.22 inch. Approximately 70 pounds of the saponiiication mixture was atomized. 'I'he contactor was vented and then the balance of the mixture was atomized. The atomized material was collected in a kettle. The temperature of the material so collected was 268 F. The collected material was then atomized at a pressure of 60G-1300 p.s.i. through a nozzle of the type shown by Figure 4. The temperature of the material entering the latter nozzle was 223 F. The product collected after the second atomization was deaerated in a Cornell cold grease homogenizer. Physical properties of the grease so prepared are tabulated below:

ASTM penetration:

14 A grease of another type and the preparation thereof is shown in the following illustrative example.

Example 7 A lithium hydroxystearate grease was prepared in the following manner.

The soap-forming ingredients, fatty acids and lithium hydroxide, and about 37 percent of the total mineral oil used, were charged to a pound capacity Stratco contactor. The batch was heated to 360 F. over a period of 1% hours. The solution temperature of a grease of the composition shown below in the tabulation is about 383 F. as indicated in Figure 6; it has no phase transition between 70 F. and the solution temperature. After saponication was complete, the contents of the contactor were atomized through a nozzle of the type shown in Figures 2 and 3, having an orilce diameter of 0.29 inch. The water content before atomization was 2.1 percent, and after was 0.20 percent (Karl Fischer method). The substantially dehydrated product was collected in a kettle, and the balance of mineral oil was added thereto at a temperature of about 300 F. The resulting product was then atomized more intensely through a nozzle of the type revealed by Figure 4 having a core with "four grooves, each groove being 0.020 by 0.035 inch in cross-section, and having an oriiice with a diameter of 0.051 inch. The pressure at the nozzle was 900-1200 p.s.i. The atomized product was cooled to F. and was deaerated. .The resulting grease had the properties shown in the following tabulation:

This was a satisfactory grease.

It is to be noted that Example 7 involves the preparation of a soap concentrate in the saponication and initial atomization operations. 1n this example about 37 percent of the total mineral oil was in the original charge; in general, this can fall within the range of from about thirty to about forty percent by weight of the total mineral oil in the grease. Thereafter, the formulation was completed by addition of the remaining oil vehicle, and the resulting product was then subjected to the more intense atomization to simultaneously eect cooling and homogenzation. This procedure can be modied by processing a soap concentrate through both atomization stages and then adding any remaining vehicle required prior to deaeration. As a further modification, part of the vehicle can be present in the saponication, another part can be added following the initial atomization, and the remaining part can later be added following the more severe atomization and prior to deaeration. Similarly, additives can be introduced at any of the stages indicated in this discussion.

FURTHER MODIFICATIONS As a further modification, with a grease having one or more phase transitions occurring between room temperature (about 7 0 F.) and solution temperature, a soap concentrate can be constituted in the saponication step and saponication can be eiected at a temperature intermediate between the solution temperature and the Yto effect further cooling and homogenization.

lowest transition temperature. This concentratecan be atomizcd at such an intermediate temperature to obtain substantiallyV complete dehydration. The dehydrated product can then be cooled through a controlled cooling cycle in a holding vessel, which can be receiver 21. The controlled cooling cycle would reduce the temperature of the dehydrated soap concentrate below the lowest transition temperature, and the time and conditions of such cooling would be sufficient to effect substantial transition of the soap thickener to the phase stable at room temperature. Part or all of the remaining Vehicle Vcan be added during or following this cooling cycle. The

resulting product Lcan then be atomized under more intense conditions at a temperature below the said lowest transition temperature. Any remaining vehicle can be added following the latter atomization prior to deaeration. Similarly, additives can be introduced at any of such stages.

Stillanother modiiication comprises preparation of a grease by using all ofthe ingredients in the saponiication mixture, with the saponification temperature being intermediate betweenY the solution temperature and the lowest transition*temperature.V They wet saponiiication mixture can be yatomized in the initial operation at such an intermediate temperature,` and therresultingV substantially de. hydrated product can be cooled'through a controlled cooling cycle as described above. The product, cooled `below-the lowest transition temperature and the soap thickener substantially in the phase stable at room tcmperature, can be atomized under more intense Yconditions Again, additives can be added at any stage of the preparation. MAlthough the invention has been illustratedhereinabove byA mineral oil Vehicles, `it is to be understood that otherl/ubricant vehicles can also be used in Vthis new manufacturing technique. t In the saponication step, it is necessary that the vehicle there used .be stableV at the operating temperatures and be resistant to saponification and hydrolysis. Typical of suchlvehicle's are mineral oils, polymerized oleiins, lsilicones, uoroc'arbon's, peruoroalkyl ethers, etc. After the`initial atomization step, these and 'other' vehiclese-can rbe',addedfsince it is no rlonger Ynecessaryl that the Vvehicle beV resistant to the saponification environment. This is primarily a` dilution stage. Such other vehicles are typiedby esters of various Ydibasic acids, esters of polyalcohols and monocarboxylic acids, silicate esters, esters of phosphorus-containing acids, amines, etc. Typical vehicles are: poly- Y.pr`opylene,polypropylene glycol, Vdi-(2-ethyl hexyD sebavcate,di-(2-ethyl'hexyl) adipate, dibutylphthalate, polyethylene glycolV di-(Z-ethyl hexoate), polymethylsiloxane.

The synthetic vehicles are most suitable for providing greases for useV in aircraft, since many of these greases .retain their lubricating value Yover a wide ,temperature range, 'from about 100 F. 'to about 500 F. Ingeneral, the mineral oils and synthetic lubricants'which can be used herein are characterized by a viscosity (S.U.V.) of greater than about 40 seconds at 100 F., preferably from about 60 to about 6,000 seconds at 1009-13.Y

While the nature of this invention has been described `in 'considerable-detail and various illustrations-have been givenf-forfimproved procedures for the preparation of lsaponifying -agent and -a fatty material-selected from the group consisting of a fattyaeidand a glyceride, saidmixture having a water content'fromab'out 0.25 to rabout120 percent by weight during soap format-ion; forming asoap thiekeningagentin situ infthe vehicle and cooling `the resultant mixture to a temperature below its solution temperature when the soap thickening agent is formed at a temperature above the solution temperature; subjecting the resulting vehicle-wet soap mixture, at'a temperature above about 250 F. and below its solution temperature, to mechanical atomization to form dispersed .droplets and instantaneously contacting the droplets directly with a surrounding atmosphere, whereupon the vehicle-wet soap mixture is substantially dehydrated; and subjecting the substantially dehydrated product, at a Vtemperature above about 220 F. and below its solution temperature, to -a more intense mechanical atomization to forindispersed droplets and instantaneouslycontacting the droplets directly with a substantially cooler surrounding atmosphere to effect heat exchange thereof. v y

2. The method of making a grease, which comprises: constituting a mixture comprising a lubricant vehicle, a saponifying agent and a fatty material selected from the group consistingV of a fatty acid and a glyceride, said mixture having a water content of from about 0.25 toV about 20 percent by weight during soap formation; forming a soap thickening agentY in'situ in the vehicle and cooling the resultant mixtureY to a temperature below its solution temperature when the soap Athickening agent is formed at artemperature above thefsrluition temperature; subjecting the resulting vehicle-wet Ysoap mixture, atV a'temperature above about 250 F. and below its solution temperature, to mechanical atomization to form dispersed droplets and instantaneously contacting the droplets directly with a surrounding atmosphere, whereupon said resulting mixture is substantially dehydrated to a water content of less than about 0.25 percent by weight; and subjecting the substantially dehydrated product, Vat a temperature above about 2207 F. and below its solution temperature, to a more intense mechanical atomization to form dispersed ,droplets and instantaneously contacting the latter droplets directly with a substantially cooler surrounding atmosphere to effect heat exchange thereof.

Y 3.l The method of claim 2 wherein the soap thickening agent is formed at va temperature below' its solution temperature. Y

4. The method of claim 2 wherein the temperature is always below the initial transition temperature .of the said soap thickening agent in the vehicle.

5. Thermethod of claim 2 wherein the temperature of the vehicle-wet soap mixture andthe temperature of the dehydrated product subjected to mechanicalatomization are below the initial transition temperature of the soap thickening agent in the vehicle.Y Y 'i 6. The method of claim A2 wherein the lubricant vehicle is mineral oil. Y l

7. The method of claim 2 wherein a mixture of soaps are formed in situ in the vehicle. Y

8. The method of claim 2 wherein the original mixture has a water content of from about 0.5 to about l0 percent by weight, and wherein said mixture is dehydrated to a water content of less than about 0.5 percent by weight.

9. The method of claim 2 wherein mechanical atomization is accomplished by spraying said vehicle-wet soap mixture through a low pressure atomizing nozzle, and by spraying said substantially dehydrated product through a high pressure atomizing nozzle. ,Y Y

10. The method of making a lithium soap grease containing a lesser quantity of calcium soap vand having a solution temperature of about 376F., which comprises: constituting a mixture of mineral Aoil, ,lithiumY hydroxide, lime and fatty material, said mixture having a water Ycontent of about one percent by weight during saponcation; forming a mixture of lithium and calcium'soaps by saponication in situ in the mineral oil at a'tenlperature below about 376 F.; subjecting the resulting mineral oil-wet soaps mixture, at artemperature above about 250 F. and below about 376 F., to Vmechanical atomization toV form dispersed droplets and instantaneously contacting the droplets with a surrounding' atmosphere, whereupon said resulting mixture is substantially dehydrated to a water content of less than about 0.25 percent by weight; subjecting the substantially dehydrated product, at a temperature above about 220 F. and below about 376 F., to a more intense mechanical atomization -to form dispersed droplets and instantaneously contacting the latter droplets with a substantially cooler surrounding atmosphere of air to effect heat exchange thereof.

l1. The method of making a lithium soap grease containing a lesser quantity of calcium soap and having a solution temperature of about 376 F., whch comprises: constituting a mixture of mineral oil, lithium hydroxide, lime and fatty material, said mixture having a water content of about one percent by weight during saponication and containing from about thirty to about forty percent by weight of the total mineral oil in the grease; forming a mixture of lithium and calcium soaps by saponication in situ in the mineral oil at a temperature (l) between about 310 F. and about 376 F.; adding the remainder of mineral oil; subjecting the resulting mineral oil-wet soaps mixture, at a temperature (2) between about 310 F. and about 376 F., to mechanical atomization to form dispersed droplets and instantaneously contacting the droplets with a surrounding atmosphere, whereupon said resulting mixture is substantially dehydrated to a water content of less than about 0.25 percent by weight; subjecting the substantially dehydrated product, at a temperature (3) above about 220 F. and below about 376 F., to a more intense mechanical atomization to form dispersed droplets and instantaneously contacting the latter droplets with a substantially cooler surrounding atmosphere of air to eect heat exchange thereof.

12. 'Ihe method of claim l1 wherein the initial mechanical atomization is conducted at a shear rate correspondi8 ing to a shear rate from about 20,000 to about 100,000 reciprocal seconds as determined in a pintle valve nozzle operated as described herein.

13. The method of forming a lithium hydroxystearate grease having a solution temperature of about 383 F., which comprises: constituting a mixture of mineral oil, lithium hydroxide, hydrogenated soya fatty acids and hydrogenated castor oil acids, said mixture having a Water content of about two percent by weight during soap formation and containing about one-third of the total mineral oil in the grease; forming lithium soaps by saponitication in situ in the mineral oil, at a temperature below about 383 F.; subjectng the resulting oil-wet soap mixture, at a temperature above about 250 F. and below about 383 F., Ito mechanical atomization to form dispersed droplets and instantaneously contacting the droplets with a surrounding atmosphere, whereupon said resulting mixture is substantially dehydrated to a water content of about 0.2 percent by weight; adding the balance of the mineral oil to the substantially dehydrated product at a temperature between about 250 F. and about 383 F.; subjecting the substantially dehydrated product, at a temperature above about 220 F. and about 383 F., to a more intense mechanical atomization to form dispersed droplets and instantaneously contacting the latter droplets directly with a substantially cooler surrounding atmosphere to eiect heat exchange thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,257,945- Fraser Oct. 7, 1941 2,433,636 Thurman Dec. 30, 1947 2,704,363 Armstrong Mar. 15, 1955 Patent Noo 2,95OH249 UNTTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION August 23Sl 1960 Eldon L Armstrong et al.l

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that 'the said Letters Patent should read as corrected below.

Signed and sealed this 4th day of April 1961.,

(SEAL) Attest ERNEST W. SWIDER X XP EETEUE w. CEOCEEE y Actingv Commissioner of Patents 

1. THE METHOD OF MAKING A GREASE, WHICH COMPRISES CONSTITUTING A MIXTURE COMPRISING A LUBRICANT VEHICLE, A SAPONIFYING AGENT AND A FATTY MATERIAL SELECTED FROM THE GROUP CONSISTING OF A FATTY ACID AND A GLYCERIDE, SAID MIXTURE HAVING A WATER CONTENT FROM ABOUT 0.25 TO ABOUT 20 PERCENT BY WEIGHT DURING SOAP FORMATION, FORMING A SOAP THICKENING AGENT IN SITU IN THE VEHICLE AND COOLING THE RESULTANT MIXTURE TO A TEMPERATURE BELOW ITS SOLUTION TEMPERATURE WHEN THE SOAP THICKENING AGENT IS FORMED AT A TEMPERATURE ABOVE THE SOLUTION TEMPERATURE, SUBJECTING THE RESULTING VEHICLE-WET SOAP MIXTURE, AT A TEMPERATURE ABOVE ABOUT 250*F. AND BELOW ITS SOLUTION TEMPERATURE TO MECHANICAL ATOMIZATION TO FORM DISPERSED DROPLETS AND INSTANTANEOUSLY CONTACTING THE DROPLETS DIRECTLY WITH A SURROUNDING ATMOSPHERE, WHEREUPON THE VEHICLE-WET SOAP MIXTURE IS SUBSTANTIALLY DEHYDRATED, AND SUBJECTING THE SUBSTANTIALLY DEHYDRATED PRODUCT, AT A TEMPERATURE ABOVE ABOUT 220*F. AND BELOW ITS SOLUTION TEMPERATURE TO A MORE INTENSE MECHANICAL ATOMIZATION TO FORM DISPERSED DROPLETS AND INSTANTANEOUSLY CONTACTING THE DROPLETS DIRECTLY WITH A SUBSTANTIALLY COOLER SURROUNDING ATMOSPHERE TO EFFECT HEAT EXCHANGE THEREOF. 